ENGLISH：

MIT researchers find timing and dosage of DNA-damaging drugs are key to whether a cancer cell dies or enters senescence.

Bendta Schroeder?|?Koch Institute

Publication Date:

July 27, 2023

Despite the proliferation of novel therapies such as immunotherapy or targeted therapies, radiation and chemotherapy remain the frontline treatment for cancer patients. About half of all patients still receive radiation and 60-80 percent receive chemotherapy.

Both radiation and chemotherapy work by damaging DNA, taking advantage of a vulnerability specific to cancer cells. Healthy cells are more likely to survive radiation and chemotherapy since their mechanisms for identifying and repairing DNA damage are intact. In cancer cells, these repair mechanisms are compromised by mutations. When cancer cells cannot adequately respond to the DNA damage caused by radiation and chemotherapy, ideally, they undergo apoptosis or die by other means.

However, there is another fate for cells after DNA damage: senescence — a state where cells survive, but stop dividing. Senescent cells’ DNA has not been damaged enough to induce apoptosis but is too damaged to support cell division. While senescent cancer cells themselves are unable to proliferate and spread, they are bad actors in the fight against cancer because they seem to enable other cancer cells to develop more aggressively. Although a cancer cell’s fate is not apparent until a few days after treatment, the decision to survive, die, or enter senescence is made much earlier. But, precisely when and how that decision is made has not been well understood.

In a?study?of ovarian and osteosarcoma cancer cells appearing July 19 in?Cell Systems,?MIT researchers show that cell signaling proteins commonly associated with cell proliferation and apoptosis instead commit cancer cells to senescence within 12 hours of treatment with low doses of certain kinds of chemotherapy.

“When it comes to treating cancer, this study underscores that it’s important not to think too linearly about cell signaling,” says Michael Yaffe, who is a David H. Koch Professor of Science at MIT, the director of the MIT Center for Precision Cancer Medicine, a member of MIT’s Koch Institute for Integrative Cancer Research, and the senior author of the study. “If you assume that a particular treatment will always affect cancer cell signaling in the same way — you may be setting yourself up for many surprises, and treating cancers with the wrong combination of drugs.”

Using a combination of experiments with cancer cells and computational modeling, the team investigated the cell signaling mechanisms that prompt cancer cells to enter senescence after treatment with a commonly used anti-cancer agent. Their efforts singled out two protein kinases and a component of the AP-1 transcription factor complex as highly associated with the induction of senescence after DNA damage, despite the well-established roles for all of these molecules in promoting cell proliferation in cancer.

The researchers treated cancer cells with low and high doses of doxorubicin, a chemotherapy that interferes with the function with topoisomerase II, an enzyme that breaks and then repairs DNA strands during replication to fix tangles and other topological problems.

By measuring the effects of DNA damage on single cells at several time points ranging from six hours to four days after the initial exposure, the team created two datasets. In one dataset, the researchers tracked cell fate over time. For the second set, researchers measured relative cell signaling activity levels across a variety of proteins associated with responses to DNA damage or cellular stress, determination of cell fate, and progress through cell growth and division.

The two datasets were used to build a computational model that identifies correlations between time, dosage, signal, and cell fate. The model identified the activities of the MAP kinases Erk and JNK, and the transcription factor c-Jun as key components of the AP-1 protein likewise understood to involved in the induction of senescence. The researchers then validated these computational findings by showing that inhibition of JNK and Erk after DNA damage successfully prevented cells from entering senescence.

The researchers leveraged JNK and Erk inhibition to pinpoint exactly when cells made the decision to enter senescence. Surprisingly, they found that the decision to enter senescence was made within 12 hours of DNA damage, even though it took days to actually see the senescent cells accumulate. The team also found that with the passage of more time, these MAP kinases took on a different function: promoting the secretion of proinflammatory proteins called cytokines that are responsible for making other cancer cells proliferate and develop resistance to chemotherapy.

“Proteins like cytokines encourage ‘bad behavior’ in neighboring tumor cells that lead to more aggressive cancer progression,” says Tatiana Netterfield, a graduate student in the Yaffe lab and the lead author of the study. “Because of this, it is thought that senescent cells that stay near the tumor for long periods of time are detrimental to treating cancer.”

This study’s findings apply to cancer cells treated with a commonly used type of chemotherapy that stalls DNA replication after repair. But more broadly, the study emphasizes that “when treating cancer, it’s extremely important to understand the molecular characteristics of cancer cells and the contextual factors such as time and dosing that determine cell fate,” explains Netterfield.

The study, however, has more immediate implications for treatments that are already in use. One class of Erk inhibitors, MEK inhibitors, are used in the clinic with the expectation that they will curb cancer growth.

“We must be cautious about administering MEK inhibitors together with chemotherapies,” says Yaffe. “The combination may have the unintended effect of driving cells into proliferation, rather than senescence.”

In future work, the team will perform studies to understand how and why individual cells choose to proliferate instead of enter senescence. Additionally, the team is employing next-generation sequencing to understand which genes c-Jun is regulating in order to push cells toward senescence.

This study was funded, in part, by the Charles and Marjorie Holloway Foundation and the MIT Center for Precision Cancer Medicine.

漢：

麻省理工學(xué)院的研究人員發(fā)現(xiàn)，DNA損傷藥物的時(shí)間和劑量是癌癥細(xì)胞死亡或衰老的關(guān)鍵。

Bendta Schroeder |科赫研究所

出版日期：

2023年7月27日

盡管免疫療法或靶向療法等新療法激增，但放射和化療仍然是癌癥患者的一線治療。大約一半的患者仍在接受放射治療，60-80%的患者接受化療。

輻射和化療都是通過(guò)破壞DNA發(fā)揮作用，利用癌癥細(xì)胞特有的脆弱性。健康細(xì)胞更有可能在輻射和化療中存活，因?yàn)樗鼈冏R(shí)別和修復(fù)DNA損傷的機(jī)制是完整的。在癌癥細(xì)胞中，這些修復(fù)機(jī)制受到突變的損害。當(dāng)癌癥細(xì)胞不能充分應(yīng)對(duì)輻射和化療引起的DNA損傷時(shí)，理想情況下，它們會(huì)發(fā)生凋亡或通過(guò)其他方式死亡。

然而，DNA損傷后的細(xì)胞還有另一種命運(yùn)：衰老——細(xì)胞存活但停止分裂的狀態(tài)。衰老細(xì)胞的DNA沒(méi)有受到足夠的損傷來(lái)誘導(dǎo)細(xì)胞凋亡，但損傷過(guò)大，無(wú)法支持細(xì)胞分裂。雖然衰老的癌癥細(xì)胞本身無(wú)法增殖和擴(kuò)散，但它們?cè)趯?duì)抗癌癥的斗爭(zhēng)中起著不良作用，因?yàn)樗鼈兯坪跄苁蛊渌┌Y細(xì)胞更積極地發(fā)育。盡管癌癥細(xì)胞的命運(yùn)在治療后幾天才明顯，但存活、死亡或衰老的決定要早得多。但是，具體何時(shí)以及如何做出這一決定還沒(méi)有得到很好的理解。

麻省理工學(xué)院的研究人員對(duì)7月19日出現(xiàn)在《細(xì)胞系統(tǒng)》雜志上的卵巢和骨肉瘤癌癥細(xì)胞進(jìn)行了一項(xiàng)研究，研究表明，通常與細(xì)胞增殖和凋亡相關(guān)的細(xì)胞信號(hào)蛋白會(huì)使癌癥細(xì)胞在接受低劑量某些化學(xué)療法治療后12小時(shí)內(nèi)衰老。

“在治療癌癥方面，這項(xiàng)研究強(qiáng)調(diào)，重要的是不要過(guò)于線性地思考細(xì)胞信號(hào)，”麻省理工學(xué)院大衛(wèi)·H·科赫科學(xué)教授、麻省理工癌癥精準(zhǔn)醫(yī)學(xué)中心主任、麻省理理工學(xué)院科赫綜合癌癥研究所成員、該研究的高級(jí)作者M(jìn)ichael Yaffe說(shuō)?！叭绻阏J(rèn)為一種特定的治療方法總是以同樣的方式影響癌癥細(xì)胞的信號(hào)傳導(dǎo)，你可能會(huì)讓自己陷入許多意外，并用錯(cuò)誤的藥物組合治療癌癥?！?/p>

“在治療癌癥方面，這項(xiàng)研究強(qiáng)調(diào)，重要的是不要過(guò)于線性地思考細(xì)胞信號(hào)，”麻省理工學(xué)院大衛(wèi)·H·科赫科學(xué)教授、麻省理工癌癥精準(zhǔn)醫(yī)學(xué)中心主任、麻省理理工學(xué)院科赫綜合癌癥研究所成員、該研究的高級(jí)作者M(jìn)ichael Yaffe說(shuō)?！叭绻阏J(rèn)為一種特定的治療方法總是以同樣的方式影響癌癥細(xì)胞的信號(hào)傳導(dǎo)，你可能會(huì)讓自己陷入許多意外，并用錯(cuò)誤的藥物組合治療癌癥。”

研究人員用低劑量和高劑量的阿霉素治療癌癥細(xì)胞，阿霉素是一種干擾拓?fù)洚悩?gòu)酶II功能的化學(xué)療法，這種酶在復(fù)制過(guò)程中斷裂并修復(fù)DNA鏈，以修復(fù)纏結(jié)和其他拓?fù)鋯?wèn)題。

通過(guò)在最初暴露后6小時(shí)至4天的幾個(gè)時(shí)間點(diǎn)測(cè)量DNA損傷對(duì)單個(gè)細(xì)胞的影響，該團(tuán)隊(duì)創(chuàng)建了兩個(gè)數(shù)據(jù)集。在一個(gè)數(shù)據(jù)集中，研究人員追蹤了細(xì)胞隨時(shí)間的命運(yùn)。在第二組中，研究人員測(cè)量了各種蛋白質(zhì)的相對(duì)細(xì)胞信號(hào)活性水平，這些蛋白質(zhì)與對(duì)DNA損傷或細(xì)胞應(yīng)激的反應(yīng)、細(xì)胞命運(yùn)的確定以及細(xì)胞生長(zhǎng)和分裂的進(jìn)展有關(guān)。

這兩個(gè)數(shù)據(jù)集用于建立一個(gè)計(jì)算模型，確定時(shí)間、劑量、信號(hào)和細(xì)胞命運(yùn)之間的相關(guān)性。該模型確定MAP激酶Erk和JNK以及轉(zhuǎn)錄因子c-Jun的活性是AP-1蛋白的關(guān)鍵成分，同樣被認(rèn)為參與衰老的誘導(dǎo)。研究人員隨后驗(yàn)證了這些計(jì)算結(jié)果，表明DNA損傷后對(duì)JNK和Erk的抑制成功地阻止了細(xì)胞進(jìn)入衰老。

雅菲實(shí)驗(yàn)室的研究生、該研究的主要作者Tatiana Netterfield說(shuō)：“細(xì)胞因子等蛋白質(zhì)會(huì)促進(jìn)鄰近腫瘤細(xì)胞的‘不良行為’，從而導(dǎo)致更具攻擊性的癌癥進(jìn)展?！??！罢?yàn)槿绱?，人們認(rèn)為衰老細(xì)胞長(zhǎng)時(shí)間停留在腫瘤附近對(duì)治療癌癥是有害的?！?/p>

這項(xiàng)研究的結(jié)果適用于用一種常用的化療方法治療的癌癥細(xì)胞，這種化療可以阻止修復(fù)后的DNA復(fù)制。但更廣泛地說(shuō)，該研究強(qiáng)調(diào)，“在治療癌癥時(shí)，了解癌癥細(xì)胞的分子特征以及決定細(xì)胞命運(yùn)的時(shí)間和劑量等背景因素極其重要，”Netterfield解釋道。

然而，這項(xiàng)研究對(duì)已經(jīng)在使用的治療方法有更直接的影響。臨床上使用了一類Erk抑制劑，即MEK抑制劑，預(yù)計(jì)它們將抑制癌癥的生長(zhǎng)。

Yaffe說(shuō)：“我們必須謹(jǐn)慎使用MEK抑制劑和化療?！?。“這種組合可能會(huì)產(chǎn)生意想不到的效果，促使細(xì)胞增殖，而不是衰老。”。

在未來(lái)的工作中，該團(tuán)隊(duì)將進(jìn)行研究，以了解單個(gè)細(xì)胞是如何以及為什么選擇增殖而不是衰老的。此外，該團(tuán)隊(duì)正在使用下一代測(cè)序來(lái)了解c-Jun正在調(diào)節(jié)哪些基因，以推動(dòng)細(xì)胞衰老。

這項(xiàng)研究部分由Charles和Marjorie Holloway基金會(huì)以及麻省理工學(xué)院癌癥精準(zhǔn)醫(yī)學(xué)中心資助。

原網(wǎng)址：https://news.mit.edu/2023/making-sense-cell-fate-0727