JOHN: TONIGHT ON "PBS NEWS WEEKEND" -- WORLD LEADERS AND THRONGS OF MOURNERS BID A SOLEMN FAREWELL TO POPE FRANCIS AS PRESIDENT TRUMP AND VLODYMYR ZELENSKYY MEET AT THE VATICAN TO DISCUSS HOPES FOR LASTING PEACE.

THEN, HOW NIH STAFFING SHORTAGES AND LAYOFFS THREATEN TO DELAY THE ROLL-OUT OF A POTENTIAL BREAKTHROUGH IN THE FIGHT AGAINST CANCER.

AND, WE EXPLORE THE WORLDWIDE CRISIS AFFECTING CORAL REEFS THAT SCIENTISTS BLAME ON GLOBAL WARMING.

>> IT'S VERY ALARMING, SO I THINK PEOPLE REALLY NEED TO RECOGNIZE WHAT THEY'RE DOING, YOU KNOW, BY THE INACTION.

IT'S THE KISS OF DEATH FOR CORAL REEFS.

♪ JOHN: GOOD EVENING.

I'M JOHN YANG.

POPE FRANCIS WAS LAID TO REST TODAY AFTER A SOLEMN REQUIEM MASS OUTSIDE ST. PETER'S BASILICA IN THE VATICAN.

OUR COVERAGE BEGINS WITH SPECIAL CORRESPONDENT MALCOLM BRABENT IN ROME.

♪ MALCOLM: BENEATH THE ROMAN SKY, A QUARTER OF THE MILLION PEOPLE WENT TO ST. PETER'S SQUARE TO GLORIFY THE FORMER ARGENTINIAN NIGHTCLUB BOUNCER WHO HISTORY WILL REMEMBER AS A POPE OF PEACE.

CAME TO PARTICIPATE IN THE GRANDEST OF FUNERAL SERVICES WITH RITUALS DATING BACK CENTURIES.

THEY SAW KINGS AND PRINCES AND PRESIDENTS TAKE THEIR PLACES BENEATH THE FIERCE APRIL SUN, INCLUDING WILLIAM, THE HEIR TO THE BRITISH THRONE.

FORMER U.S. PRESIDENT JOE BIDEN AND HIS WIFE JILL.

OPPOSITE THE BISHOPS AND CARDINALS WHO WILL BE SEQUESTERED TO CHOOSE THE NEXT POPE.

FRANCIS WAS UNIVERSALLY ACCLAIMED AS AN EXTRAORDINARY PONTIFF.

IN KEEPING WITH HIS PEACELOVING SPIRIT, BEHIND THE SCENES, THERE WAS A SIGNIFICANT ATTEMPT TO BROKER A TRUCE BETWEEN UKRAINE AND ITS RUSSIAN INVADERS.

BEFORE PAYING HIS RESPECTS TO THE COFFIN, PRESIDENT TRUMP SAT DOWN WITH UKRAINE PRESIDENT ZELENSKYY FOR THE FIRST TIME SINCE THE RANCOROUS CONFRONTATION IN THE OVAL TWO MONTHS AGO.

TRUMP REPORTEDLY PRESSURED ZELENSKYY TO ACCEPT A PLAN IN WHICH UKRAINE WILL FORMERLY SURRENDER TERRITORY OCCUPIED BY RUSSIA, INCLUDING THE CRIMEAN PENINSULA, AS WELL AS GRANTING THE UNITED STATES AN ENORMOUS STAKE IN UKRAINE'S MINERAL WEALTH.

AS FAR AS THE WHITE HOUSE IS CONCERNED, THIS IS THE ONLY FEASIBLE DEAL.

ON THE X SOCIAL MEDIA PLATFORMS, 70 DESCRIBED THE MEETING AS SYMBOLIC AND POTENTIALLY HISTORIC.

HE SAID HE WAS HOPING FOR RESULTS ON EVERYTHING COVERED IN THEIR DISCUSSIONS.

PROTECTING THE LIVES OF UKRAINIANS, A FULL AND UNCONDITIONAL CEASE-FIRE, AND A RELIABLE AND LASTING PEACE THAT WOULD PREVENT ANOTHER WAR FROM BREAKING OUT.

IN A POST ON HIS TRUTH SOCIAL NETWORK, PRESIDENT TRUMP LAUNCHED A BROADSIDE AGAINST RUSSIA'S PUTIN.

HE SAID THERE WAS NO REASON TO SHOOT MISSILES INTO CIVILIAN AREAS.

IT MAKES ME THINK, HE SAID, THAT MAYBE PUTIN DOES NOT WANT TO STOP THE WAR AND IS JUST TAPPING ME ALONG.

WHEN TRUMP EMERGED, HE WAS MET WITH SILENCE.

A CONTRAST WITH ZELENSKYY'S APPEARANCE COULD NOT HAVE BEEN GREATER.

WARM APPLAUSE GREETED THE UKRAINIAN PRESIDENT WHEN HE TOOK HIS SEAT.

THEN, THE GRAND CEREMONY BEGIN IN EARNEST WITH THE COFFIN CARRIED FROM THE BASILICA INTO THE SQUARE.

THE CONGREGATION WAS ADDRESSED BY A 91-YEAR-OLD ITALIAN CARDINAL.

>> IN THIS MAJESTIC ST. PETER'S SQUARE WHERE POPE FRANCIS CELEBRATED THE EUCHARIST SO MANY TIMES AND PRESIDED OVER GREAT GATHERINGS OVER THE PAST 12 YEARS, WE ARE GATHERED WITH SAD PARTS AND PRAYER AROUND HIS MORTAL REMAINS.

MALCOLM: TALKED ABOUT PEACE IN UKRAINE, DOMINATING THE DIPLOMATIC AGENDA.

THE CARDINAL REMINDED THE THRONG OF THE FUTILITY OF WAR.

>> FACED WITH THE RAGING WARS OF RECENT YEARS WITH THEIR INHUMAN HORRORS AND COUNTLESS DEATHS AND DESTRUCTION, POPE FRANCIS INCESSANTLY RAISED HIS VOICE IMPLORING PEACE.

WAR, HE SAID, IS ONLY THE DEATH OF PEOPLE AND THAT INSTRUCTION OF HOMES -- THE DESTRUCTION OF HOMES, HOSPITALS AND SCHOOLS.

MALCOLM: AND THEN PRESIDENT TRUMP'S WAR ON THE MEXICAN BORDER.

>> WAR ALWAYS LEAVES THE WORLD WORSE THAN BEFORE.

IT IS ALWAYS A PAINFUL AND TRAGIC DEFEAT FOR EVERYONE.

BUILD BRIDGES, NOT WALLS WAS AN EXHORTATION HE REPEATED MANY TIMES.

MALCOLM: IN CONCLUSION, CARDINAL RAY APPEALED TO POPE FRANCIS IN THE AFTERLIFE.

>> POPE FRANCIS USED TO CONCLUDE HIS SPEECHES AND HIS PRIVATE MEETINGS BY SAYING DO NOT FORGET TO PRAY FOR ME.

NOW, DEAR POPE FRANCIS, WE ASK YOU TO PRAY FOR US AND WE ASK YOU FROM HEAVEN TO BLESS THE CHURCH, BLESS ROME, AND BLESS THE WHOLE WORLD.

MALCOLM: AFTER COMMUNION AND AN INDICATION, THE FUNERAL SERVICE CAME TO AN END.

THE COFFIN WAS PLACED ON A MODIFIED POPE MOBILE AND DRIVEN THROUGH THE STREETS FOR FRANCI'' FINAL EARTHLY JOURNEY.

THE COFFIN WENT PAST SOME OF ROME'S MOST FAMOUS LANDMARKS INCLUDING THE COLISEUM.

TENS OF THOUSANDS OF PEOPLE STOOD SEVERAL ROWS DEEP TO SAY FAREWELL.

FRANCIS IS THE FIRST POPE IN MORE THAN A CENTURY TO BE LAID TO REST OUTSIDE THE VATICAN.

THOUSANDS CLUSTERED AROUND THE BASILICA SANTA MARIA TO WITNESS THE CLIMAX OF AN EMOTIONAL DAY.

CONSISTENT WITH HIS COMMITMENT TO THE POOR AND DISPOSSESSED, FRANCIS INVITED REFUGEES, PRISONERS, TRANSSEXUALS, AND OTHERS IN NEED TO BE HIS ULTIMATE GUARD OF HONOR BEFORE THE VATICAN'S MASTER OF CEREMONIES BLESSED THE TOMB AND PLACED A SEAL ON THE COFFIN.

A GUARD GAVE A FINAL SALUTE AND FRANCISCUS WAS LEFT AT PEACE AMONG HIS PEOPLE AND WITH HIS GOD.

FOR PBS NEWS WEEKEND, I'M MALCOLM BRABENT IN ROME.

JOHN: TODAY'S FUNERAL AND BURIAL MARK THE BEGINNING OF NINE DAYS OF OFFCIAL MOURNING AT THE VATICAN.

CARDINALS WILL LEAD MASSES EACH DAY.

AND THE WORDS OF THEIR HOMILIES, THEIR REFLECTIONS ON THE SCRIPTURE READINGS THAT DAY, WILL UNDOUBTEDLY BE CLOSELY EXAMINED AND ANALYZED FOR CLUES ABOUT WHAT'S ON THEIR MINDS AS THEY PREPARE TO ELECT A NEW POPE.

JOHN ALLEN HAS COVERED THE VATICAN FOR 30 YEARS.

HE'S EDITOR OF "CRUX," AN ONLINE SITE THAT COVERS THE VATICAN AND THE CATHOLIC CHURCH.

PRACTICALLY ALL THE CARDINALS WHO ARE ELIGIBLE TO VOTE, THE CARDINALS WERE UNDER THE AGE OF 80, WERE AT TODAY'S FUNERAL.

THEY WILL BE AT ROME LEADING UP TO THE CONCLAVE.

IN THOSE DAYS, WILL THE BE TALKING TO EACH OTHER FORMERLY OR INFORMALLY ABOUT WHO THEY MIGHT SEE AS THE NEXT POPE?

JOHN A.: ABSOLUTELY, THEY WILL BE TALKING TO ONE ANOTHER ABOUT WHO THEY SEE IS THE NEXT POPE.

THAT IS THE BUSINESS THEY HAVE BEEN CALLED TO ROME TO PERFORM.S SO, IN THESE DAILY MEETINGS OF CARDINALS, ALL THE GENERAL CONGREGATION MEETING, SOME OF THAT IS PROCEDURAL BUT SOME OF IT ALLOWS CARDINALS THE OPPORTUNITY TO TALK TO ONE ANOTHER ABOUT WHAT THEY SEE IS THE ISSUES FACING THE CHURCH TO SORT THROUGH WHERE THE CHURCH STANDS AND WHERE THESE CARDINALS BELIEVE IT NEEDS TO GO.

JOHN Y.: THIS TIME RIGHT NOW, WHAT ARE SOME OF THE CONSIDERATIONS THE CARDINALS WILL BE THINKING ABOUT?

JOHN A.: FUNDAMENTALLY, THE ISSUE THAT IS FACING EVERY CONCLAVE IS THE WANT TO KEEP GOING IN TERMS OF THE PAPACY THAT JUST ENDED OR DO YOU WANT TO TRY SOMETHING ELSE?

BEYOND THAT, THERE IS A COMPLICATED SORT OF BUSHEL BASKET FULL OF ISSUES THEY WILL BE LOOKING AT.

FROM GEOPOLITICS OR ENTERING AN ERA WHERE ALL THE ALLIANCES SEEM TO BE FALLING APART AND NEW ONES ARE COMING INTO VIEW.

THEY WANT SOMEBODY WHO CAN STEER THE CHURCH SAFELY THROUGH THOSE STORMS.

INTERNAL CHURCH DEBATE OVER CONTENTIOUS MATTERS SUCH AS WOMEN AND OUTREACH TO THE LGBTQ+ COMMUNITY, TO MORE BROAD SOCIAL CONCERNS LIKE MIGRATION AND POVERTY.

TRYING TO COME TO SOME SORT OF ROUGH CONSENSUS AND WHEN YOU HAVE 135 ALPHA MALES WITH STRONG IDEAS ABOUT THE CHURCH REACHING THAT KIND OF COMPROMISE, THAT IS A DELICATE ART.

JOHN Y.: THE VIEWERSHIP OF THE MOVIE CONCLAVE SPIKED AFTER POPE FRANCIS' DEATH.

YOU HAVE WRITTEN A BOOK ABOUT CONCLAVES.

HOW CLOSE IS IT TO WHAT ACTUALLY HAPPENS?

JOHN A.: I HAVE BEEN TELLING PEOPLE THAT TAKING THE MOVIE CONCLAVE AS A GUIDE TO A REAL PAPAL ELECTION IS LIKE TAKING THAT ZANY 1980'S SPACE COMEDY "SPACE BALLS" AS A GUIDE FOR SPACE.

THIS IS REAL WORLD POLITICS WHERE EVERYTHING IS FAR MORE INDIRECT AND SUBTLE.

LET'S NOT BE NAIVE.

THERE IS REAL POLITICAL SAUSAGE BUT THIS IS NOT THE IOWA CAUCUS.

THIS IS POLITICS VATICAN STYLE.

JOHN Y.: DO CARDINALS GO INTO A CONCLAVE WITH A CANDIDATE IN MIND OR A GROUP OF CANDIDATES IN MIND?

JOHN A.: OFTEN, CARDINALS DO FILE INTO THE SISTINE CHAPEL WITH A FAIRLY STRONG SENSE FOR WHOM THEY INTEND TO CAST THEIR VOTE.

THE LAST TWO CONCLAVES, THE CONCLAVE IN 2005 THAT ELECTED POPE BENEDICT XVI AND THE CONCLAVE THAT ELECTED POPE FRANCIS, BOTH OF THOSE WERE OVER IN ABOUT A DAY AND A HALF.

THAT WOULD BE COMPLETELY IMPOSSIBLE IF IT WEREN'T FOR THE FACT THAT A NUMBER OF CARDINALS HAD MADE UP THEIR MINDS BEFORE THEY ACTUALLY WENT INTO THE SISTINE CHAPEL ABOUT WHICH WAY THEY WANT TO GO.

JOHN Y.: I KNOW YOU SAID THIS IS NOT THE IOWA CAUCUSES, BUT IS IT POSSIBLE TO HANDICAP THE LIKELY FOLKS WHO COULD BE POPE?

JOHN A.: THERE'S AN OLD ROMAN SAYING THAT HE WHO ENTERS A CONCLAVE AS A POPE EXITS AS A CARDINAL.

MEANING SOMETIMES GETTING THAT KIND OF TALK DOES YOU MORE HARM THAN GOOD.

THAT SAID, THEY CAN LOOK AT THE REPUTATIONS CARDINALS HAVE HELD OVER THE YEARS.

THE SIGNIFICANCE OF THE POSITION , THE JOB THAT THEY HAVE HELD.

ONE ODDS ON FAVORITE, AND SOMEBODY WHO CERTAINLY WILL GET A VERY SERIOUS LOOK, WOULD BE THE ITALIAN CARDINAL, WHO WAS THE SECRETARY OF STATE.

THE TOP DIPLOMAT UNDER POPE FRANCIS, WHO WOULD BE SEEN A SOMEBODY WHO WOULD IN SOME WAYS CARRY FORWARD THE FRANCIS LEGACY, BUT IS AN EXTRAORDINARILY STABLE, CAREFUL, MEASURED MAN.

GIVEN WHAT'S HAPPENING IN THE WORLD, I THINK A NUMBER OF CARDINALS MIGHT FIND THAT ATTRACTIVE.

JOHN Y.: JOHN ALLEN IN ROME, THANK YOU VERY MUCH.

JOHN A.: YOU'RE WELCOME.

JOHN: IN TONIGHT'S OTHER NEWS, THERE WAS A EXPLOSION AT A PERSIAN GULF PORT IN SOUTHERN IRAN.

AT LEAST FIVE PEOPLE WERE KILLED AND MORE THAN 700 OTHERS INJURED.

PLUMES OF BLACK SMOKE COULD BE SEEN FOR MILES.

THE CAUSE OF THE BLAST IS UNKNOWN.

ACCORDING TO A PRIVATE SECURITY FIRM, LAST MONTH, A SHIPMENT OF A CHEMICAL ROCKET FUEL FOR MISSILES WAS DELIVERED TO THE PORT.

IRAN HAS NOT COMMENTED ON THAT.

THE EXPLOSION CAME ON THE SAME DAY OF A THIRD ROUND OF TALKS BETWEEN THE UNITED STATES AND IRAN ON TEHRAN'S RAPIDLY ADVANCING NUCLEAR PROGRAM.

U.S. OFFICIALS SAID THE TALKS IN OMAN WERE PRODUCTIVE AND THAT THERE WOULD BE ANOTHER SESSION SOON IN EUROPE.

INDIA SAID PAKISTANI SOLDIERS SHOT AT INDIAN POSTS FOR A SECOND-STRAIGHT NIGHT IN THE DISPUTED KASHMIR REGION, FUELING LONG-STANDING TENSIONS BETWEEN THE TWO NATIONS.

IT COMES IN THE WAKE OF A GUN ATTACK EARLIER THIS WEEK IN KASHMIR THAT KILLED DOZENS OF PEOPLE, MOSTLY INDIAN TOURISTS.

INDIA BLAMES PAKISTAN FOR THE INCIDENT, CALLING IT AN ACT OF TERRORISM.

PAKISTAN DENIES ANY INVOLVEMENT.

BOTH PAKISTAN AND INDIA CLAIM THE ENTIRE KASHMIR REGION AND HAVE FOUGHT WARS OVER IT.

A FEDERAL JUDGE WANTS THE TRUMP ADMINISTRATION TO EXPLAIN WHY A TWO-YEAR-OLD U.S. CITIZEN WAS DEPORTED TO HONDURAS WITH HER MOTHER AND OLDER SISTER.

LAWYERS FOR THE GIRL SAY SHE, HER MOTHER, AND HER 11-YEAR-OLD SISTER WERE DETAINED WHEN THEY SHOWED UP AT AN ICE OFFICE ON THURSDAY FOR A ROUTINE APPOINTMENT.

WHEN THE GIRLS' LEGAL CUSTODIAN, A U.S. CITIZEN, WENT TO FEDERAL COURT SEEKING THEIR RELEASE, ADMINISTRATION LAWYERS CLAIMED THE MOTHER WANTED HER DAUGHTERS TO GO WITH HER.

JUDGE TERRY DOUGHERTY ASKED TO SPEAK WITH THE MOTHER ABOUT HER WISHES, BUT WAS TOLD THEY HAD ALREADY BEEN RELEASED IN HONDURAS.

DOUGHERTY, A TRUMP APPOINTEE, ORDERED A HEARING IN THREE WEEKS "IN THE INTEREST OF DISPELLING OUR STRONG SUSPICION THAT THE GOVERNMENT JUST DEPORTED A U.S. CITIZEN WITH NO MEANINGFUL PROCESS."

AND VIRGINIA GIUFFRE, A KEY FIGURE IN THE JEFFREY EPSTEIN SEX TRAFFICKING CASE, HAS DIED.

GIUFFRE WAS AMONG THE FIRST SURVIVORS OF EPSTEIN'S ABUSE TO GO PUBLIC AND PRESS FOR HIS CRIMINAL PROSECUTION.

SHE CLAIMED THAT WHEN SHE WAS A TEENAGER, EPSTEIN FORCED HER TO HAVE SEX WITH BRITAIN'S PRINCE ANDREW.

BOTH MEN DENIED THE CLAIM.

ANDREW EVENTUALLY SETTLED WITH GIUFFRE, INCLUDING DONATING AN UNDISCLOSED SUM TO THE ORGANIZATION SHE FOUNDED FOR SURVIVORS OF SEXUAL ABUSE.

GIUFFRE'S FAMILY SAID SHE DIED BY SUICIDE.

SHE WAS 41 YEARS OLD.

IF YOU OR SOMEONE YOU KNOW IS STRUGGLING WITH THOUGHTS OF SELF-HARM, YOU CAN CALL OR TEXT THE NATIONAL SUICIDE HOTLINE AT 988.

STILL TO COME ON "PBS NEWS WEEKEND," HOW STAFFING CUTS AT NIH MAY DELAY THE IMPLEMENTATION OF A PROMISING DEVELOPMENT IN THE FIGHT AGAINST CANCER.

AND, A NEW REPORT SAYS CORAL BLEACHING IS AFFECTING VIRTUALLY ALL OF THE WORLD'S REEFS.

♪ JOHN: EARLIER THIS MONTH, DOCTORS AT THE NATIONAL INSTITUTES OF HEALTH MADE A PROMISING STEP IN THE FIGHT AGAINST CANCER.

IN A PAPER PUBLISHED IN "NATURE MEDICINE," AN IMMUNOTHERAPY TREATMENT WHICH USES THE BODY'S OWN DEFENSES WAS ABLE TO SHRINK GASTROINTESTINAL TUMORS FOR ABOUT A QUARTER OF PATIENTS.

BUT HIH STAFFING SHORTAGES, LAYOFFS AND CUTS ARE THREATENING TO DELAY THE IMPLEMENTATION OF THIS PROMISING DEVELOPMENT.

WILLIAM BRANGHAM RECENTLY SPOKE WITH DR. STEVE ROSENBERG, WHO HELPED PIONEER THAT TREATMENT ABOUT THIS PRECARIOUS MOMENT FOR FEDERALLY-FUNDED SCIENCE.

WILLIAM: SO GOOD TO HAVE YOU ON THE PROGRAM, DR. ROSENBERG.

YOU HAVE BEEN WORKING IN THIS FIELD OF IMMUNOLOGY FOR A VERY LONG TIME.

FOR PEOPLE WHO HAVE NOT BEEN FOLLOWING CANCER RESEARCH AS CLOSELY AS YOU HAVE, HELP US UNDERSTAND HOW SIGNIFICANT A DEVELOPMENT WAS THIS?

DR. ROSENBERG: WE'VE HAD THREE EFFECTIVE WAYS TO TREAT CANCER OVER THE PREVIOUS DECADES.

SURGERY, RADIATION AND CHEMOTHERAPY.

THE BEST APPLICATION OF THOSE TREATMENTS CAN CURE OVER HALF OF EVERYONE WHO DEVELOPS CANCER NOW.

BUT, THE ABILITY OF CANCER TO SPREAD TWO DIFFERENT SITES STILL IS A MAJOR PROBLEM IN OVER 600,000 AMERICANS WHO DIE EVERY YEAR OF CANCER UNLESS WE DEVELOP BETTER TREATMENTS.

RATHER THAN USING SCALPELS, RADIATION BEAMS AND DRUGS, WE ARE TRYING TO TAKE ADVANTAGE OF THE BODY'S OWN IMMUNE SYSTEM WHICH RECOGNIZES A CANCER IS FOREIGN BUT NOT FOREIGN ENOUGH TO REJECT IT.

OUR GOAL IS TO STIMULATE THE IMMUNE SYSTEM TO BE STRONG ENOUGH TO GET RID OF THE CANCER AND THAT APPROACH IS CALLED IMMUNOTHERAPY.

WILLIAM: THIS TECHNIQUE SHOWED PROMISE IN ABOUT A QUARTER OF THE TUMORS.

WHO WERE THE PATIENT'S MOST BENEFITING FROM THIS?

WHAT WERE THEY SUFFERING FROM?

DR. ROSENBERG: WE HAVE DEVELOPED IMMUNOTHERAPIES OVER THE YEARS.

IT WAS APPROVED BY THE FOOD AND DRUG ADMINISTRATION.

WE FIRST DID THIS WITH MELANOMA WHERE WE DID GET GOOD TUMOR REGRESSIONS IN 66% OF PATIENTS WHO HAD METASTATIC DISEASE.

BUT, THAT APPROACH HAS NOT PROVEN EFFECTIVE FOR PATIENTS WITH A COMMON SOLID CANCER THAT RESULT IN 90% OF ALL DEATHS FROM CANCER.

BY THAT, I MEAN TUMORS FROM THE RECTUM, THE COLON, THE STOMACH, THE UTERUS, THE OVERRATE.

Y.

BY DEVELOPING TECHNIQUES, WE HAVE BEEN ABLE TO CONSISTENTLY, OR AT LEAST A QUARTER OF THE TIME, SEE REGRESSIONS OF METASTATIC CANCER.

ALL THE PATIENTS WE TREAT AT THE NATIONAL CANCER INSTITUTE HAVE BEEN THROUGH ALL STANDARD TREATMENTS AND COME HERE TO THE NIH, THE NATIONAL INSTITUTES OF HEALTH, AS A LAST RESORT TO RECEIVE NEW TREATMENTS AND HELP US DEVELOP NEW APPROACHES TO PATIENTS WITH CANCERS THAT CANNOT BE SOLVED BY TODAY'S MEDICINES.

WILLIAM: I WONDER AS SOMEONE WHO HAS BEEN IN THIS FIELD, TO HAVE THIS -- AGAIN, THIS KIND OF PROGRESS TO BE MADE, HOW DOES THAT FEEL TO YOU PERSONALLY AS A RESEARCHER AND A DOCTOR?

DR. ROSENBERG: IT'S A ROLLER COASTER.

I WILL WALK INTO ONE ROOM WHERE WE TREATED PATIENTS -- I MAKE ROUNDS EVERY DAY -- TREATED PATIENTS WHO HAVE HAD A GOOD RESPONSE AND THEY ARE HAPPY AND THEIR FAMILY IS HAPPY.

AND THEN WALK INTO THE NEXT ROOM AND THINGS HAVE NOT WORKED AND THE PATIENTS AND THEIR FAMILY ARE IN TEARS BECAUSE, IN FACT, IT IS THE LAST HOPE AND IT HAS NOT HELPED THEM.

SO, IT'S A ROLLER COASTER OF EMOTIONS.

WHAT KEEPS ALL OF US WORKING DAY AND NIGHT TO TRY TO DEVELOP BETTER TREATMENTS.

THE NATIONAL INSTITUTES OF HEALTH IS A WORLD'S GREATEST RESEARCH INSTITUTION.

IT HAS A 250-BED HOSPITAL IN WHICH WE CAN TRADE PATIENTS.

IT IS SURROUNDED BY RESEARCH LABORATORIES.

MY OWN LABORATORY IS YARDS AWAY FROM THE WARD.

IT IS IN THOSE RESEARCH LABORATORIES THAT THESE SCIENTIFIC FINDINGS ARE MADE AND THEN TRANSLATED INTO PATIENTS.

THE MANDATE OF THE NIH IS NOT ONLY TO PROVIDE THE BEST OF TODAY'S MEDICINE BUT TO PRODUCE THE MEDICINE OF TOMORROW.

WILLIAM: TO THAT ROLLER COASTER EXPERIENCE YOU ARE DESCRIBING, AS YOU KNOW, THIS IS A VERY FRAUGHT TIME FOR FEDERALLY FUNDED SCIENCE IN THIS COUNTRY ESPECIALLY AT THE NIH.

LAYOFFS, BUDGET CUTS, ETC.

WHAT HAS THAT MEANT FOR YOUR WORK SPECIFICALLY?

DR. ROSENBERG: I HAVE BEEN DOING THIS FOR MANY DECADES AT THE NIH.

THESE ARE THE MOST DIFFICULT TIMES WE HAVE EVER HAD, I HAVE EVER EXPERIENCED.

WE'VE HAD A HIRING FREEZE WHICH PREVENTS US FROM HIRING INDIVIDUALS.

UP UNTIL JUST LAST WEEK, WE WERE NOT ABLE TO PLACE ORDERS FOR MATERIALS.

THAT HAS BEEN RELAXED TO SOME EXTENT, BUT IT IS STILL QUITE LIMITING BECAUSE THE ENTIRE ACQUISITIONS DEPARTMENT, THE PEOPLE WHO PLACE THE ORDERS FOR THE NATIONAL CANCER INSTITUTE HAVE BEEN TERMINATED.

SO, IT IS A DIFFICULT TIME.

NFORTUNATELY, THESE PROBLEMS HAD US TO DELAY PATIENT TREATMENTS BUT WE ARE CONTINUING TO WORK.

BUT, BUDGET CUTS ARE SLOWING DOWN THE RESEARCH, NO QUESTION ABOUT THAT.

WILLIAM: WHAT DOES THAT AND DO - - HOW IS MORALE AROUND THE NAH RIGHT NOW?

-- NIH RIGHT NOW?

DR. ROSENBERG: WE HAVE A DEDICATED GROUP OF PEOPLE WORKING HERE.

MANY OF OUR STAFF HAVE BEEN WITH ME FOR OVER 10 YEARS TRYING TO SOLVE THESE PROBLEMS.

THESE ARE DIFFICULT TIMES BECAUSE A LOT OF MY FELLOW SCIENTISTS WERE UP FOR RENEWAL AND THERE'S NO GUARANTEE THEY ARE GOING TO BE RENEWED AS FAR AS THESE BUDGET CUTS.

SO, THERE'S A LOT OF ANXIETY RIGHT NOW ABOUT OUR ABILITY TO CONTINUE MAKING PROGRESS AT THE PACE THAT WE WISH.

WILLIAM: THAT IS DR. STEVE ROSENBERG AT THE NATIONAL CANCER INSTITUTE AT THE NIH.

SO GOOD TO SPEAK WITH YOU.

THANK YOU VERY MUCH FOR YOUR TIME.

DR. ROSENBERG: MY PLEASURE.

♪ JOHN: FINALLY TONIGHT, A LOOK UNDER THE SEA.

CORAL REEFS ARE A CRUCIAL PART OF THE MARINE ECOSYSTEM, PROVIDING HABITATS FOR ALL SORTS OF MARINE LIFE AND PROTECTING COASTLINES FROM STORM DAMAGE.

BUT AS ALI ROGIN REPORTS, SCIENTISTS SAY RISING OCEAN TEMPERATURES ARE POSING A GRAVE THREAT TO THE FUTURE OF THE WORLD'S REEFS.

ALI: THE MALDIVE ISLANDS IN THE INDIAN OCEAN ARE THE PICTURE OF PARADISE.

BUT BENEATH THE AQUA BLUE WATER, THERE'S A CRISIS UNFOLDING.

ONCE VIBRANT, CORAL REEFS HAVE LOST THEIR COLORS IN WHAT SCIENTISTS SAY IS PART OF THE WORST GLOBAL BLEACHING EVENT ON RECORD, IMPACTING MORE THAN 80 COUNTRIES AND TERRITORIES.

A REPORT FROM THE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION REVEALED THAT 84% OF THE PLANET'S CORAL REEFS HAVE BEEN HIT.

THE SMITHSONIAN'S MELANIE MCFIELD SAYS THE BLEACHING IS TRIGGERED BY PROLONGED EXPOSURE TO ELEVATED OCEAN TEMPERATURES DUE TO HUMAN-CAUSED CLIMATE CHANGE.

MELANIE: IT'S VERY ALARMING, SO I THINK PEOPLE REALLY NEED TO RECOGNIZE WHAT THEY'RE DOING, YOU KNOW, BY THE INACTION.

IT'S THE KISS OF DEATH FOR CORAL REEFS.

ALI: THIS IS NOT THE FIRST MASS EVENT OF ITS KIND.

IT'S THE FOURTH KNOWN WIDESPREAD BLEACHING OF CORAL REEFS, BUT THE TROUBLING PART MCFIELD SAYS IS THAT THESE EPISODES KEEP GETTING WORSE.

CORAL REEFS ARE KNOWN AS THE RAINFOREST OF THE SEA BECAUSE OF THEIR BIODIVERSITY.

BUT SCIENTIST MARK EAKIN SAYS OCEAN TEMPERATURES AREN'T EXPECTED TO COOL ANYTIME SOON.

AND UNTIL THEY DO, THE HEAT STRESS ON CORALS COULD LEAD TO PERMANENT DAMAGE OR KILL THE REEFS ALTOGETHER.

MARK: WE JUST MAY NEVER SEE THE HEAT STRESS THAT CAUSES BLEACHING DROPPING BELOW THE THRESHOLD THAT TRIGGERS A GLOBAL EVENT.

SO, THIS MAY BE THE LAST ONE.

ALI: IF CORAL REEFS DIE, SO COULD NEARLY A QUARTER OF ALL SEA LIFE, WHICH FEED MILLIONS AND SUSTAIN INDUSTRIES FROM FISHING TO TOURISM.

BUT THE GOOD NEWS IS THAT CORALS ARE RESILIENT AND CAN RECOVER IF CONDITIONS ALLOW.

IN THE DEPTHS OFF THE FLORIDA KEYS, WHERE WATER TEMPERATURES EXCEEDED 100 DEGREES FAHRENHEIT IN JULY 2023, EFFORTS TO TRY TO RESTORE DAMAGED CORAL ARE UNDERWAY.

RESEARCHERS TEND NURSERIES IN IN THE DEEPER, COOLER WATER WHERE CONDITIONS HELP SPROUT NEW BUDS.

THEY'RE THEN CLIPPED AND PRESERVED WITH THE GOAL OF ONE DAY TRANSPLANTING THEM BACK INTO THE OCEAN TO HELP JUMPSTART NEW GROWTH.

MARK EAKIN SAYS THESE EFFORTS ARE PROMISING, BUT THE LARGER, GLOBAL SOLUTION HINGES ON REDUCING SEA TEMPERATURES AND THOSE EFFORTS START ON LAND.

MARK: THE BEST WAY TO PROTECT CORAL REEFS IS TO ADDRESS THE ROOT CAUSE OF CLIMATE CHANGE AND THAT MEANS REDUCING THE EMISSIONS.

THAT'S THE BIGGEST PART.

EVERYTHING ELSE IS LOOKING MORE LIKE A BAND-AID RATHER THAN A SOLUTION.

ALI: FOR NOW, SCIENTISTS ARE URGENTLY SOUNDING THE ALARM AS THE WORLD'S CORAL REEFS ARE BEING PUSHED INTO UNCHARTED TERRITORY.

MARK: WE'RE LOOKING AT SOMETHING THAT'S COMPLETELY CHANGING THE FACE OF OUR PLANET.

ALI: FOR PBS NEWS WEEKEND, I'M ALI ROGIN.

♪ JOHN: THAT IS "PBS NEWS WEEKEND" FOR THIS SATURDAY.

I'M JOHN YANG.

FOR ALL OF MY COLLEAGUES, THANKS FOR JOINING US.

SEE YOU TOMORROW.

♪ [CAPTIONING PERFORMED BY THE NATIONAL CAPTIONING INSTITUTE, WHICH IS RESPONSIBLE FOR ITS CAPTION CONTENT AND ACCURACY.]